Autofocus & Focus Techniques

Also known as: AF techniques, manual focus, focus tracking, back button focus
Related techniques: Macro Photography, Wide-Angle Photography, Close-Focus Wide-Angle

Overview

Achieving accurate focus is one of the most fundamental challenges in underwater photography. The underwater environment degrades autofocus performance through reduced contrast, lower light levels, monochromatic blue-green coloring, and the optical effects of dome and flat ports. As Wetpixel editor Adam Hanlon argued on Wetpixel Live, a camera’s ability to achieve autofocus underwater is “one of the most important criteria that should be considered when choosing a camera for underwater use” (^[1]). The community’s discussions about focus techniques span the entire Wetpixel archive from 2003 through 2023, reflecting two decades of evolving camera technology and hard-won practical experience.

History & Development

Early Digital Era: Manual vs. Auto (2003-2006)

When digital SLRs first entered underwater housings, many photographers carried over manual focus habits from the film era. In a foundational July 2003 Wetpixel forum thread on focus tips, James Wiseman advised macro shooters: “For shooting macro in surge: forget about autofocus. Use manual focus and set it at your minimum focusing distance (max magnification)… then move in and out until the subject appears in focus in your viewfinder. BLAM!” He also noted that for macro with autofocus in bright light and calm conditions, the technique was to “autofocus on the animal and half press or focus lock button on the subject. If it’s a small fish, you probably autofocused on the body, so move back a little until the eyes are in focus” (^[2]).

ChrisG agreed with the manual focus approach, noting that at close range it was “generally not possible to have the subject entirely in focus” and that the photographer “must decide which pieces of the animal should be the sharpest.” He challenged anyone to show him a “properly focussed subject on the scale of a pygmy seahorse at >1:1 with autofocus” (^[3]).

However, Alex Mustard represented a different approach from the start. In the same 2003 thread, he stated: “After reading the above posts I fear I am a lazy photographer! I always use autofocus on continuous servo because even if the fishy is still I rarely am!” He found Nikon’s off-center AF sensors particularly helpful for focusing on fish eyes and preferred to concentrate on composition rather than manual focus mechanics (^[4]).

ScorpioFish offered an experienced perspective, stating: “Reality is that I can’t do better than the cameras AF. I’ve tried it with the 200mm macro.” He advocated using focus lock as “an acquired skill” — pointing at the desired focus spot such as an eyeball, locking, recomposing, and firing. He also described a useful hybrid technique: “Another technique is to AF on something in the distance range you want to shoot. Flick MSC to manual and reposition camera until you get the target in focus and fire.” His broader philosophy was telling: “Alex says lazy. Maybe I’m lazy, too. But the reality is that as soon as quit messing with camera settings, my composition improved” (^[5]).

Stewart L Sy reported success using AF tracking with even tiny subjects like pygmy seahorses: “I set my camera on focus tracking, therefore I will close in on the seahorse then once the camera locks on… the camera will do a great job tracking the subject.” His reasoning was straightforward: “if the camera can track a speeding race car, why can’t it compensate for the slight movement of surge, breathing, darting anemone fish?” Craig countered that the answer was “lack of light, contrast, viz and depth of field” (^[6]).

DavePHDV was among the earliest Wetpixel forum members to describe back button focus underwater in 2003: “I always use AF. Set it on continuous. With the D100’s menu I set the back button to auto focus. Focus with the back lever and when my subject is in focus hit the trigger” (^[7]).

By 2005, AF had become standard for many underwater DSLR shooters, though beginners arriving from film cameras were still surprised it worked underwater at all. As Mustard explained to one forum newcomer: “AF can work very well underwater. And I use it for all my pictures. It is not an automatic cure, though. You must understand how it works and help it along” (^[8]). Derway recommended the Sony V3 compact as having “far away the best AF in any digicam, near 0 final press shutter lag” for non-DSLR shooters (^[9]).

Also in 2005, Alex Mustard posted about the upcoming Nikon D200 AF system, citing a French magazine review that called the new AF module “simply amazing in focusing in low light and subjects with low contrast,” noting that “AF is one of the few aspects of performance that you can judge from the spec sheet” (^[10]).

The Manual Focus Macro Debate (2005-2010)

A persistent debate ran through the Wetpixel forums over whether to use autofocus or manual focus for macro photography with 100mm/105mm lenses. In a January 2005 thread, users like Rand (randapex) preferred manual focus for stationary subjects like nudibranchs and pygmy seahorses, finding AF “searching” too disruptive: “It drives me nuts to have the lens zooming in and out searching for the subject.” He described manual tracking as “kinda like skeet shooting” (^[11]).

Craig agreed that he “rarely use[d] AF with macro regardless of lens,” finding it worked “best with larger subjects and with the 50/60mm lenses.” He noted that with Canon equipment, the situation was somewhat better: “Properly set up, a Canon rig takes away much of the penalty associated with AF but I still don’t like it. I just hate it a lot less” (^[12]).

Forum member Frogfish offered a nuanced counterpoint: he used autofocus when he could, aided by a focusing light even in daylight to reduce hunting. He used “a Hartenberger mini with a wide-angle reflector on top of the housing.” But he identified two situations where manual focus was essential: “One is shooting in very shallow water and bright sunlight, where you get little ripples of dark and light passing over the subject. It sends the little autofocus brain in the camera into catatonic shock or something.” The other was “when the subject is partially obscured at least some of the time by things in front of its plane — commensals in a crinoid, shrimps or whatever in bushy black coral or sea whips” (^[13]).

Kasey highlighted the camera-dependence of the choice: “I shot exclusively manual with my D100 and Aquatica housing — largely for the same reason that robert shoots AF. It was difficult to see.” After switching to an F100 in a Seacam housing with better viewfinder optics, he moved to mainly AF: “The focusing ability of the camera is also much better in low light than my D100 was — especially in the peripheral sensors. I never thought I would switch to AF for macro, but I love it!” (^[14]).

The Canon vs. Nikon AF/MF Switch Problem

The practical ability to switch between AF and MF underwater depended heavily on equipment design. Nikon camera bodies had an AF/MF switch on the body, accessible through most housings. Canon placed the switch on the lens barrel, which was typically covered by the focus gear inside the housing. As Tom Kline explained: “There is no Canon camera body counterpart to the MF-AF switch found on Nikon camera bodies. Instead, EF lenses have an AF-MF switch on the lens itself — a fundamental difference between Nikon and Canon” (^[15]).

This design difference made Canon shooters develop workarounds. Gudge described using a custom mode setting on the Canon 7D where “Metering Start only is assigned to shutter release at half press” — effectively decoupling AF so manual focus could be used, with the “focus now button on the back” available for AF when needed (^[16]).

Subal offered a premium solution for Nikon shooters: a dedicated flat port for the Nikon 105mm VR with both an AF/MF housing switch and a manual focus control dial. User timg reported: “A switch on the housing flips the camera between AF and MF — and then a control dial on the port allows the lens to be focussed manually. It works a treat” (^[17]).

Stewart L Sy described the Aquatica approach for Canon USM lenses: “Any USM EF lens can be over ridden using the MF ring on the lens. I use this method using my Aquatica housing. I have the AF/MF Macro port. If I want to use MF, then I turn the external knob on the port body” with back button AF allowing instant return to autofocus (^[18]).

Early Back Button Focus Discussions (2006-2007)

The concept of back button focus — decoupling AF from the shutter button — appeared in Wetpixel forums well before it became widely popularized. In a February 2006 thread, Ryan posed the question of whether to route AF-ON or AF-L/AE-L to the housing handle button. Karl Dietz emphasized the importance for continuous AF shooters: “I exclusively shoot AF-C and the AF-On button is my preferred way to activate focus tracking. If I shot in AF-S, I’d probably go for the AE/AF button. For AF-C shooters this control is used for EVERY shot” (^[19]).

In 2007, Steve Dingeldein described a technique he learned from Nikonians.org: using AF-C with shutter priority release, combined with the AF-ON button, to create a “quasi-manual” system. Once focused via the back button, “pushing the shutter button will not cause it to try to refocus” — essentially the back button focus technique that would become standard practice (^[20]).

The DSLR Autofocus Maturity (2008-2016)

The Nikon D300 (2007) marked a significant autofocus improvement for underwater photographers. In a June 2008 forum thread, Tom R1 described his plan to experiment with the D300’s AF-C mode with 3D tracking and 51 AF points to follow moving macro subjects. Steve Dingeldein, who had just returned from Little Cayman with a D300, reported: “The autofocus was MUCH better with the D300 in my opinion. I shot AF-C, focus priority, area autofocus with 21 sensors. My 105VR used to hunt a LOT with the D200 but though it did some hunting with the D300 it was uncommon.” He found the “low light focusing was great with very little hunting” and concluded: “I now feel that I am the limiting factor by far in terms of getting good underwater photos” (^[21]).

Chris (Undertow) offered valuable advice on tracking settings: with focus tracking ON, “the camera will continue to ‘expect’ the focus point to be where it was before the distance suddenly changed” — preventing the camera from refocusing on a passing fish. He recommended continuous release mode for “2-3 frames” to catch the right pose (^[22]).

The Canon EOS 5D presented AF challenges for early adopters. In 2006, Greg Williams described the classic dome port focusing problem: his 5D “had a really hard time focusing underwater” with a 24-85mm lens behind a dome port. James Wiseman diagnosed the issue: “You’re described the classic symptoms… the dome port acts as a strong negative diopter” (^[23]).

The Nikon D850 represented a major leap. In a 2020 thread, phxazcraig compared it to his previous D810 for macro with the 105VR: “Depth of field: 1/4 inch. Diver movement during shot: 4 feet. With the D810 I’d try to keep the focus point on the subject, surge in and hit the shutter release, fingers crossed the focus would be achieved in time. I once took 31 shots and only got 2 in focus. Then I switched to the D850. Now I no longer bother with 30 attempts — the success ratio was about 31 out of 31” (^[24]).

Hanlon compared using the D850 in single servo mode to “driving a Ferrari at 30mph,” advocating: “For the majority of my shooting, I use Continuous AF with 3D focus tracking. 3D tracking allows the camera to use color and exposure information, along with the phase and contrast detection sensors in the AF and image sensors. Effectively, it allows it to use its whole soft and hardware to achieve focus” (^[25]).

OneyellowTang confirmed the D850’s prowess, noting the D500 was “slightly ‘faster’” for macro due to “the slightly more cropped view enabling the AF to lock on the subject slightly more easily.” He reported the D850 “really shines in W/A shooting with the WACP — I don’t believe I’ve had it lock on anything but the primary subject on dozens of dives” (^[26]).

Adam Hanlon also published a detailed review of Reikan FoCal Pro AF calibration software in 2014, demonstrating that lens-body AF fine-tuning was becoming important as sensor resolutions increased. He tested it with a Nikon D810 and found that each lens took “around 5-6 minutes to test,” with the Sigma 15mm f/2.8 requiring a +6 adjustment — “not imply[ing] that the lens (or camera) are in any way faulty, simply that the combination requires this setting in order to offset minute manufacturing tolerance differences.” He concluded: “If you are shooting any camera with 20+ megapixels, it is likely that lens calibration will improve your images.” Forum commenter Roger McLennan confirmed the value for Canon 5D Mark III and 6D users (^[27]).

Mirrorless AF: Promise and Reality (2012-2023)

The transition from DSLRs to mirrorless cameras introduced entirely new autofocus technologies underwater, with mixed results initially.

Contrast detection AF — used by early mirrorless cameras and Panasonic’s Micro Four Thirds line — worked by analyzing image contrast on the sensor. While accurate, it was slower than DSLR phase detection. However, as Interceptor121 noted in 2020, cameras using only contrast detection (like Panasonic models) were immune to the PDAF-related image artifacts that affected on-sensor phase detection systems (^[28]).

Phase detection AF in DSLRs required a dedicated AF sensor and a translucent section of the camera’s mirror. As a 2018 Wetpixel article noted: “Phase detection is only available in SLR cameras, as it requires a dedicated AF sensor and a translucent section of the camera’s mirror, which are both components you will not find in a mirrorless camera” (^[29]). However, manufacturers soon began embedding phase detection pixels directly on the imaging sensor, creating on-sensor phase detection AF (OSPDAF).

Canon’s Dual Pixel AutoFocus (DPAF), introduced on the Canon EOS 70D, was an on-sensor phase detection system used “when shooting either in Live View or video modes.” Canon later incorporated DPAF into the 7D Mark II, 5D Mark IV, and Cinema EOS cameras including the C100, C300, and C300 Mark II (^[30]).

Despite marketing claims of superior AF performance, many mirrorless cameras underperformed underwater compared to DSLRs. Mustard noted in his 2023 Sony a7R V review: “Since the first Mirrorless cameras appeared, they have been accompanied by the claims of great feats of autofocus. Olympus claimed that the original E-M5 had the world’s fastest autofocus, but it was clear, underwater at least, it was a long way off that generation of SLRs. And this failure to live up to the marketing is something that many underwater photographers have reported” (^[31]).

The Panasonic GH4, tested underwater by Russ Sanoian of Backscatter in 2014, showed visible focus hunting in macro video. Sanoian himself was “impressed with the cameras ability to lock and maintain focus with such a shallow depth of field” using the Olympus 60mm macro with Nauticam SMC, but commenter Jeffrey Honda observed the camera “seems to be searching in and out a lot” and concluded that “auto focus in this mode” didn’t look “viable” (^[32]).

A technical concern with on-sensor phase detection was raised by forum member Interceptor121 in November 2020: the AF pixels could cause visible artifacts including striping, banding, and fixed-pattern noise. He described three distinct issues: “1. Lens internal reflections are aggravated and take a grid shape where the AF pixels are located. 2. In certain situations you have PDAF striping where you can see stripes in the frame aligned with the AF pixels. 3. In other cases of low light you also have banding.” He noted that this “issue is common to different level of gravity among all cameras that use a Sony sensor and therefore includes Sony, Nikon and Olympus cameras. Other cameras that only have contrast detect and use same sensor like Panasonic are immune.” Nikon Z6/Z7 cameras were identified as “the worst offenders” because Nikon’s attempt to fix striping introduced banding (^[33]).

Interceptor121 supported his analysis with data from Bill Claff of Photons to Photos, reporting that a camera with PDAF scored 22% DSNU (dark signal non-uniformity) compared to 6% for a contrast-detect-only model sharing the same sensor. Claff confirmed: “The PDAF pixels are different and certainly can cause more noise particularly Fixed Pattern Noise (FPN). I think there’s a limit to how well any firmware can ‘fix’ the effect” (^[34]).

Hanlon responded with genuine engagement, noting: “I’m unclear how phase detect in an SLR with a separate phase detect sensor (i.e. not on-sensor) would produce the result? The AF sensor data is separate from the imaging sensor” — correctly distinguishing between DSLR and mirrorless AF architectures (^[35]).

The Sony a7R V (2023) represented a breakthrough. In his extensive 40-dive review, Mustard declared it “the best-focusing camera I have used underwater” — the first time he made that claim about a mirrorless camera over any SLR. The camera’s AF was “driven by a new processor, a generation on from that the a7R IV” with “next generation EVF and Autofocus tech from its big brother the a1.” He used AF-C throughout, “with Wide area for wide angle and Zone (a smaller, moveable area) the rest of the time.” For macro, he “favored Zone for shooting fish portraits but also liked Expanded Spot” (^[36]).

The camera’s AI-driven subject recognition could identify fish approximately 40% of the time, though Mustard found the general tracking so effective that dedicated subject recognition modes were “pretty unnecessary”: “The camera has a seemingly intelligent ability to correctly guess what the subject of the frame is and to keep it in focus.” The tracking was “so sticky that if another subject (say another fish in a group) moves to the front of the composition the camera will often resolutely ignore it, keeping the now obscured original subject in sharp focus” (^[37]).

However, AF performance still degraded in darker, more monochromatic underwater conditions: “The autofocus advantage of a7R V reduces noticeably as underwater levels reaching the sensor get darker, less contrasty and more monochromatic. In bright reef conditions the Sony a7R V focuses markedly better than my SLR, but in darker, more monochromatic places, its advantage diminishes.” Adapted lenses performed worse — the Canon 8-15mm fisheye on a Metabones adapter was “definitely much more prone to hunting.” Mustard found that “using the lens on back button focus and only focusing when I needed to was the best cure for the hunting issue” (^[38]).

Techniques & Methods

Single AF (AF-S / One Shot)

The most basic mode: the camera locks focus when the shutter button is half-pressed and holds it. Widely used for macro photography of stationary or slow-moving subjects. The photographer can focus-and-recompose — locking focus on the subject’s eye, then shifting the frame for better composition before firing.

In a 2023 poll on Wetpixel, single AF remained the most commonly used mode for wide-angle photography. Interceptor121 elaborated: “Unless I am shooting moving dolphins I use single AF for wide angle including slow moving subjects.” Floris Bennema described his approach: “If its a non moving subject I take the time to move the AF-point to it. Otherwise I… focus S-AF with the object in the middle and then re-frame without additional focusing” (^[39]).

Continuous AF (AF-C / AI Servo)

The camera continuously adjusts focus as long as the shutter button is half-pressed or the AF-On button is held. Essential for moving subjects like pelagic fish, sharks, and dolphins. The Nikon D300 and later Nikon DSLRs offered 3D tracking within continuous AF, using color information to follow a subject across the frame.

Hanlon described using “AF-C 3D AF for pretty much everything since the D810,” finding it “so good, there is no real reason to change. Continuous AF (along with back button activation) allows easy recomposition with wide angle images and compensates for any lack of (my) stability in the water” (^[40]).

PhxAzCraig used the same approach on both D850 and Z9: “back button focus with the camera set to use 3D Tracking. Basically it’s a single point that is supposed to grab onto whatever object you put it on and keep tracking it as long as you hold the AF-ON button down” (^[41]).

Architeuthis (Wolfgang) used C-AF with tracking on the Olympus EM-1 II for wide-angle, finding it “very reliable for WA, even with adapted Canon 8-15 and Tokina 10-17 lenses” though it “works so-so for macro and is very difficult to use with 60mm+CMC-1” (^[42]).

Interceptor121 cautioned against blind trust in continuous AF: “CAF moves the lens based on what it thinks will happen… It may have unpredictable results when the focus motor steps are set for what the camera thinks will happen on land or with a flat port. The camera specifically may go hunting when it predicts focus. With single AF there is no prediction” (^[43]).

Back Button Focus (BBF)

Back button focus decouples autofocus activation from the shutter release button, assigning it instead to the AF-On button (or a remapped rear button) operated by the thumb. This technique became one of the most discussed topics on Wetpixel, with a dedicated article in 2016 and a Wetpixel Live episode in 2021 featuring Hanlon and Mustard (^[44], ^[45]).

Key advantages for underwater photography:

• Focus lock without recomposition hassle: The photographer can lock focus and release the thumb, then fire multiple shots without the camera refocusing. As StuartV explained: “I can get focused at the distance I’m shooting for and then stop focusing and just shoot, without worrying about the focusing system suddenly refocusing on (for example) a bait fish that just happens to swim by in the foreground” (^[46]).
• Instant switch between AF and MF: Simply stop pressing the back button and focus stays locked — effectively manual focus without flipping a switch. This solved the Canon housing problem where the lens AF/MF switch was inaccessible (^[47]). Mustard agreed this was “a good point. That BBF is good both in situations where the lens struggles to focus. And also with lenses that struggle to focus!” (^[48]).
• Dual-purpose buttons: Advanced users like StuartV programmed separate rear buttons for different AF area modes — “AF-On button programmed to use Spot Focus w/Tracking” for specific subjects like sharks, and “AEL button programmed to temporarily… switch to a Focus Area of Zone and then engage the AF” for surprise encounters needing quick response (^[49]).
• WACP compatibility: For Canon shooters using the Nauticam WACP, forum member helgromite noted that “the lens behind the WACP-1 is an old, clunky Canon lens (28-70mm f3.5-4.5) which is not that fast. I’ve often gotten out of focus shots when using only the shutter lever, where it couldn’t focus fast enough before the shutter opened” — making BBF essential (^[50]).

Phil Rudin described an advanced Sony A7c/A-1 configuration combining shutter AF with tracking-enabled back button: “the shutter depress can get you into the area you want to go very quickly and the back button can then lock onto an eye and move with that eye around the frame very quickly. Once you have locked onto a subject the difference is that it can follow the movement not just stay focused on the same plane” (^[51]).

As Steve Simon explained in his Petapixel article linked by Wetpixel, back button focus allows the photographer to “lock focus at a specific point or track moving subjects by keeping the button depressed (this works really well with 3D or AI Servo Modes)” (^[52]).

Manual Focus with Focus Peaking

Mirrorless cameras introduced focus peaking — a real-time overlay showing which parts of the image are in focus, typically highlighted in a chosen color. This transformed manual focus from a guessing game through viewfinders into a precise technique. Mustard noted in his Sony a7R V review that some photographers “rave about shooting manual focus with focus peaking indicator color, that stands out well on the underwater scene, showing exactly when the features you want are perfectly sharp” (^[53]).

On the Olympus EM-1 II, ChrisRoss reported using C-AF “in combo with back button focus” but noted that “you can assign peaking to one of the Fn buttons, but it’s not always easy to see and doesn’t stay on.” He found peaking useful on land but “haven’t found it useful UW as yet” (^[54]).

Interceptor121 used a different approach: “For shots that are not super macro I use single point AF… However that does not tell me if I have reached maximum magnification for that I use manual focus there is a guide that tells me if I am at the closest focus point and then with peaking and magnify I steady myself” (^[55]).

For compact cameras like the Sony RX100 series, the DMF (Direct Manual Focus) mode allowed photographers to start with autofocus and then fine-tune manually. When using close-up lenses like the Nauticam CMC, the recommended technique was to “set the manual focus to minimum distance and then move the camera until you see peaking working then shoot.” Interceptor121 acknowledged it was “painful but it works — i have shot videos of Pygmy sea horses with this technique” (^[56]).

The Rock-and-Fire Technique

One of the oldest underwater macro techniques, predating digital cameras: set focus to a fixed distance (often minimum focus distance for maximum magnification), then physically rock the camera forward and backward until the subject appears sharp, and fire. James Wiseman described this in 2003: “Use manual focus and set it at your minimum focusing distance (max magnification)… then move in and out until the subject appears in focus in your viewfinder. BLAM! Fire off the shot” (^[57]).

This technique remained relevant in 2020. John Liddiard described a refined version: “With every camera I have owned, autofocus in macro has locked on just behind where I would ideally like the focus to be… Hence even in good conditions, I lock focus and then rock back a fraction to get the desired focal point. For a sequence of pics, I focus, lock or disable AF, then rock to get desired focus for each pic” (^[58]).

Atus combined the technique with back button focus for close-up lens work: “When using close up lens I normally set the focus with the AF without the close up lens and after I put the close up lens and set the focus manually by moving the camera forward backward” (^[59]).

Focus for Wide-Angle and Over-Under Shots

Wide-angle focusing underwater involves the complication of dome port optics. A dome port creates a virtual image much closer to the camera than the actual subject. As forum member Cerianthus explained: “The image that the camera focuses on is a virtual image at a distance of about 1.5x the diameter of the dome” (^[60]).

For split (over-under) photography, achieving focus in both halves of the image requires careful use of hyperfocal distance. Forum member ChrisRoss provided detailed calculations in a 2022 thread: with a 16mm lens on full-frame behind an 8” dome, “the underwater portion you need to have the virtual image fall within the depth of field and the virtual image is 3 dome radii from the dome. For an 8” dome that might be as small as 300mm away.” At f/22 and approximately 0.4m focus distance, “you are in focus from 0.2m to infinity” (^[61]).

PeteAtkinson described a practical approach: selecting the aperture, then testing on land by taking a series of photos at incrementally closer manual focus distances to find “how close can you focus and still get acceptable sharpness in your background.” He then recommended taping the lens at this position for underwater use (^[62]).

Hanlon preferred using back button focus for over-unders: “I just move my focus point underwater, focus underwater using the button and then release it. This will then hold the focus point. I use depth of field to get the surface elements of the image in focus.” He also noted that “fisheye lenses tend to work better for me aesthetically” and that “big domes help, as they make it easier to deal with any ripples etc. in the water’s surface” (^[63]).

Interceptor121 added technical context: “Due to dome port optics something at 3x radius from the dome surface is already at infinity. Normally around 30cm. Depth of field is an issue for the land part not for the underwater part.” He noted that “the magic number for a 16mm lens” on full frame was f/20, especially with smaller domes (^[64]).

Focus Stacking Underwater

A February 2023 forum discussion explored whether in-camera focus stacking was feasible underwater. TImg noted you would “need to use a tripod” based on his land experience, while ChrisRoss analyzed the Olympus OM-1’s potential: “The OM-1 is capable of focus stacking handheld as it has a very fast frame rate, probably is limited by the need to limit shutter speed to 1/100 which is the sync speed for flash with electronic shutter UW.” He estimated that “in a low surge environment with 1/100 SS and a fairly sedentary subject a 3 or 4 frame stack at f5.6 might be feasible handheld.” Hyp suggested it would “only work with a video light” (^[65]).

Forum member Altsaint reported success with an Olympus EM1 Mark II using a constant ring light source in July 2023, though with caveats: “Two issues do emerge though… Firstly, the end stacked result is a jpg. Secondly, all that extra detail that comes into focus includes background and backscatter!” He found that the stacking mode’s bidirectional focus adjustment was “a bit more flexible” than bracketing, which only moved “from existing point to infinity” (^[66]).

Equipment

Focus Lights

Focus lights became essential underwater photography accessories, providing the contrast and illumination needed for camera AF systems to lock on in dim or monochromatic conditions. As Mustard wrote in his 2010 SOLA 600 review: “The importance of a focus light for underwater photography is entirely dependant on what you shoot. If you favour shooting large pelagics in the open ocean or wide angle scenics on a shallow Red Sea reef, they are thoroughly unnecessary. But if you like macro, murky water or night diving then a good focus light can make the fundamental difference between getting a shot and missing out” (^[67]).

Norwegian photographer Christian Skauge told Mustard that “in his home waters, he always encourages new shooters to purchase a decent focus light for their compact cameras, before even buying a strobe. There is no point taking photos if the camera cannot focus!” (^[68]).

Evolution of focus lights:

• Early solutions: Standard diving torches with narrow beams — functional but requiring constant re-aiming, and “with a focussed bright spot of light, we are more likely to spook critters as they are suddenly exposed to the full glare on our approach,” as Mustard noted. Another common solution was using strobe modeling lights (like those on the Ikelite DS-125). In a 2005 night focusing thread, Alex Mustard confirmed: “I always use AF at night. Works fine as long as you have a well aimed modelling light” (^[69], ^[70]).
• Fisheye FIX lights (2004 onwards): The Fisheye FIX range “caused a mainstream switch from small diving torches to dedicated focus lights among serious shooters,” as Mustard noted. They produced wide, soft beams eliminating constant re-aiming. James Wiseman wrote the original Wetpixel review in 2004. The FIX lights “raised the financial stakes, taking focus lights from the sub $100 USD realm to that of several 100” (^[71]).
• Light & Motion SOLA 600 (2010): Mustard called it “my favourite underwater photography accessory of the last 12 months.” About half the size of FIX lights, sealed and rechargeable, with both white and red light modes. The red light mode “minimised disturbance to shy marine life while still providing enough contrast for AF systems.” Both the SOLA 600 and FIX LED 500 produced “excellent white light illumination, with wide soft illumination” (^[72]).
• Hanlon’s 2011 comparison: Hanlon reviewed the SOLA 600 alongside the iTorch Pro 3, noting: “The development and profusion of Light Emitting Diode (LED) lighting has really changed the number and performance of available models. LEDs provide long battery burn times, high performance and durability.” Both lights featured red light modes “which allows the torch to assist AF with minimum impact on subjects that may become skittish when a ‘white’ light torch beam is shined on them” (^[73]).
• Inon LF1300-EWf (2017): Featured a shutter-linked auto-off function: “On-board incident light sensor detects flashing from built-in flash/external strobe to trigger this feature to shut off the light in sync with the shutter release and turns ON again automatically to avoid exposure of the light itself on an image or backscatter by not illuminating suspended particles.” The cut-off was “only 0.2 seconds not to lose your subject.” Also included a Dome Red Filter for shooting “shy marine subject without disturbing their behaviors” (^[74]).

In 2006, Willy Volk linked to Brad Brown’s comprehensive focus light comparison on Backscatter, described as “the mother of all focus light overviews” — comparing beam qualities, sizes, weights, and battery lives across six models. The extensive comment discussion revealed the popularity of budget alternatives like the Fantasea 44LED for compact camera users, with JackConnick calling it “smaller than 2x miniQ lights and with a wide, bright beam” at only $75 (^[75]).

A Wetpixel Live episode in 2020, featuring Hanlon and Mustard, covered focus light selection, noting that “most underwater photographers tend to buy focus lights as one of their early purchases” (^[76]).

AF Calibration Tools

As camera resolutions increased, lens-body autofocus calibration became important. Hanlon reviewed the Reikan FoCal Pro software in 2014, which automated the process of finding the optimal AF micro-adjustment setting for each lens-body combination. The software “uses control software to take control of the camera and shoot a series of images of a calibration target at different AF fine tuning increments while tethered to a computer.” Hanlon found it “simple and quick to use” and that “high resolution cameras will really show when a lens is not performing correctly.” Forum commenter Roger McLennan confirmed the value for Canon 5D Mark III and 6D users (^[77]).

Lens Adapters and AF

The Megadap ETZ11 adapter, shipping in 2021, enabled autofocus with Sony E-mount lenses on Nikon Z cameras, supporting “AF-S, AF-C, AF-F, Eye-AF and Face detection” with “smooth focusing performance during video shooting.” Megadap recommended: “For optimal focusing performance, Pinpoint AF mode should be avoided. AF-C wide-area focus mode should be selected for high-speed continuous shooting” (^[78]).

However, adapted lenses generally underperformed native lenses for AF. Mustard found the Canon 8-15mm fisheye on a Metabones adapter “definitely much more prone to hunting for focus, doing this regularly, while other lenses hardly ever hunted.” He hypothesized that “several factors may be responsible: we can expect any lens on an adaptor to underperform, the adaptor might not be right up to date losing performance, I shot the fisheye deeper on the walls (more monochromatic, more diffuse light reaching the sensor)” (^[79]).

Post-Focus Technology

In 2015, Panasonic released a firmware update enabling “Post-Focus” on the GX8, G7, and FZ300. This feature allowed users to “change the focus point post capture” by shooting “video at 4K with a variety of focus points that can be selected and images with different focus points saved” (^[80]).

Key Discussions

• “Tips and Tricks for Focusing” (2003) — foundational thread with James Wiseman, Alex Mustard, ScorpioFish, and DavePHDV debating manual vs. autofocus approaches and establishing the core techniques (^[81])
• “D200 Autofocus” (2005) — Alex Mustard reports on the D200’s AF system promise based on French magazine review (^[82])
• “100/105mm Macro Users Using Manual Focus?” (2005) — detailed community discussion of when to use MF vs. AF for macro, with practical housing-specific advice from Rand, Craig, Frogfish, and Kasey (^[83])
• “AF-L/AE-L or Thumb Actuated Focus, Which one?” (2006) — early back button focus discussion for Nikon shooters, with Karl Dietz advocating AF-On for AF-C users (^[84])
• “5D Autofocus Underwater” (2006) — classic dome port AF failure diagnosis for Canon 5D users (^[85])
• “Dissociating Focus from Shutter” (2007) — early description of the back button focus technique for Nikon D200 underwater (^[86])
• “D300 Autofocus Experiment” (2008) — user comparing D200 and D300 AF systems underwater, documenting the significant improvement (^[87])
• “Best way to achieve tack sharp focus” (2013) — dome port virtual image explanation, focus light recommendations for Canon 5D II users (^[88])
• “Switching from autofocus to manual focus underwater” (2015) — Canon vs. Nikon AF/MF switch design comparison, Subal and Aquatica solutions (^[89])
• “Mirrorless Focusing” (2015) — practical tips for Sony RX100 and compact camera AF with close-up lenses, DMF mode (^[90])
• “Autofocus Setup for D850 While Shooting Macro” (2020) — detailed D850 AF-C tracking configuration, D810-to-D850 improvement testimonials, Hanlon’s “Ferrari at 30mph” analogy (^[91])
• “Macro Focusing Techniques” (2020) — wide-ranging thread with Hanlon, Interceptor121, ChrisRoss, Architeuthis, and others comparing single AF, continuous AF, manual focus, and focus peaking across Nikon, Olympus, and Canon systems (^[92])
• “Side effects of mirrorless on sensor phase detect autofocus” (2020) — Interceptor121’s technical analysis of PDAF artifacts with data from Bill Claff (^[93])
• “Wetpixel Live: Back Button Autofocus” (2021) — forum discussion following the Wetpixel Live episode, with StuartV’s dual-button AF configurations and Phil Rudin’s Sony tracking setup (^[94])
• “Over-under focus technique” (2022) — hyperfocal distance calculations, dome port considerations, tape-the-focus-ring technique (^[95])
• “Is anybody using focus stacking/bracketing underwater?” (2023) — OM-1 capabilities, strobe sync speed limitations, Altsaint’s EM1 II experiments (^[96])
• “Poll: Achieving Focus in Wide Angle Shots” (2023) — poll and discussion revealing single AF remained dominant, with Hanlon and phxazcraig advocating 3D tracking (^[97])

Notable Practitioners

• Alex Mustard — consistent AF advocate since 2003, reviewer of focus lights and AF systems, wrote the definitive Sony a7R V AF assessment declaring it “the best-focusing camera I have used underwater”
• Adam Hanlon — Wetpixel editor, champion of 3D Continuous AF (“driving a Ferrari at 30mph” if using AF-S on the D850), authored multiple AF tutorials and the Reikan FoCal review
• James Wiseman — established the rock-and-fire technique in the foundational 2003 focus thread, reviewed the original Fisheye FIX focus light in 2004
• ScorpioFish — early advocate of AF for everything including macro with 105mm and 200mm lenses, developed the focus-lock-recompose workflow
• Steve Perry (Backcountry Gallery) — wildlife photographer whose Nikon autofocus tutorials were recommended by Wetpixel, referenced by D850 users (^[98], ^[99])
• Interceptor121 — prolific forum contributor who provided deep technical analysis of AF systems, OSPDAF artifacts, and focus techniques across camera platforms, collaborating with Bill Claff on sensor data analysis
• StuartV — developed advanced dual-button AF configurations for Sony cameras, enabling rapid switching between Spot/Tracking and Zone AF modes

Timeline

• 2003-07: James Wiseman, Alex Mustard, ScorpioFish, and others debate manual vs. autofocus techniques for underwater macro in foundational Wetpixel thread. DavePHDV describes early back button focus on D100 (^[100])
• 2004: Fisheye FIX focus light range launches, causing “a mainstream switch from small diving torches to dedicated focus lights” (^[101])
• 2005-01: Forum thread debates manual vs. autofocus for 100/105mm macro lenses; Rand, Craig, and Frogfish offer detailed practical advice (^[102])
• 2005-04: Forum thread “AF? Autofocus? You’re kidding!” — beginner discovers AF works underwater, Alex Mustard explains capabilities (^[103])
• 2005-06: DSLR night focusing thread discusses using strobe modeling lights and dive torches for AF assist (^[104])
• 2005-11: Mustard reports on D200’s promising AF system from French magazine review (^[105])
• 2006-02: Back button focus debate for Nikon D200 housing users — AF-ON vs. AF-L/AE-L button routing (^[106])
• 2006-04: Canon 5D AF failure underwater diagnosed as dome port virtual image issue (^[107])
• 2006-10: Brad Brown publishes comprehensive focus light comparison on Backscatter, linked by Wetpixel (^[108])
• 2007-05: Back button focus technique described as “dissociating focus from shutter” for Nikon D200 users (^[109])
• 2008-06: D300 autofocus experiments show major improvement over D200 for underwater macro, with “MUCH better” low-light AF (^[110])
• 2010-08: Alex Mustard reviews Light & Motion SOLA 600 focus light with red light mode (^[111])
• 2011-07: Hanlon reviews SOLA 600 and iTorch Pro 3 focus lights, noting LED revolution in focus lighting (^[112])
• 2014-07: Russ Sanoian tests Panasonic GH4 autofocus underwater at Backscatter; commenter finds macro video AF hunting not “viable” (^[113])
• 2014-09: Hanlon reviews Reikan FoCal Pro AF calibration software, finding Sigma 15mm needed +6 adjustment on D810 (^[114])
• 2015-04: Forum thread reveals Canon vs. Nikon AF/MF switch design differences; Subal and Aquatica solutions described (^[115])
• 2015-05: Wetpixel links Steve Perry’s Nikon autofocus tutorial; Hanlon notes 3D Continuous focus is “an excellent choice for underwater macro shooting” (^[116])
• 2015-11: Panasonic releases Post-Focus firmware for GX8/G7/FZ300, allowing focus point selection after capture (^[117])
• 2015-11: Mirrorless focusing thread discusses Sony RX100 focus peaking and DMF mode for CMC super-macro (^[118])
• 2016-04: Wetpixel links Steve Perry’s autofocus troubleshooting tutorial covering calibration, dirty sensors, and wrong AF modes (^[119])
• 2016-08: Wetpixel publishes back button autofocus overview with resources from Steve Simon, Steve Perry, Canon, and Mike Hagen (^[120])
• 2017-06: Canon explains Dual Pixel AutoFocus system, an on-sensor phase detection system used in 70D, 7D Mark II, 5D Mark IV, and Cinema EOS (^[121])
• 2017-10: Inon announces LF1300-EWf focus light with shutter-linked auto-off function and red filter (^[122])
• 2018-07: Wetpixel links phase detection AF explainer, noting it requires dedicated sensor and mirror in SLRs (^[123])
• 2020-03: D850 macro AF thread: phxazcraig reports 31/31 keeper rate vs. 2/31 on D810; Hanlon calls AF-S on D850 “driving a Ferrari at 30mph” (^[124])
• 2020-08: Wetpixel Live episode on buying a focus light, with Hanlon and Mustard (^[125])
• 2020-09: Wetpixel Live Ep 58: “Essential Guide to Camera Autofocus” by Hanlon (^[126], ^[127])
• 2020-11: Interceptor121 raises concerns about on-sensor phase detection AF artifacts (striping, banding) in mirrorless cameras, with Bill Claff data (^[128])
• 2020-12: Wide-ranging macro focusing techniques thread: Hanlon advocates 3D Continuous AF on D500/D850; debate across Nikon, Olympus, Canon systems (^[129])
• 2021-02: Wetpixel Live Ep 141: “Back Button Autofocus Advice”; StuartV describes dual-button AF configurations; Phil Rudin describes Sony tracking setup (^[130], ^[131], ^[132])
• 2021-08: Megadap ships Sony E-to-Nikon Z autofocus adapter with AF-S, AF-C, Eye-AF support (^[133])
• 2022-08: Over-under focus technique thread: ChrisRoss provides hyperfocal calculations, PeteAtkinson describes tape-the-ring method (^[134])
• 2023-02: Alex Mustard publishes Sony a7R V review, calling it “the best-focusing camera I have used underwater” — first mirrorless to surpass SLR AF in his experience (^[135])
• 2023-02: Focus stacking underwater explored; OM-1 identified as best candidate, Altsaint reports success with EM1 II using constant light (^[136])
• 2023-03: Wide-angle focus poll reveals single AF remains dominant; Hanlon and phxazcraig advocate 3D tracking with back button focus (^[137])

References

Wetpixel Live